1. Field of the Invention
The present invention relates to a method for rapidly identifying porcine estrogen receptor (ESR) marker at a low cost. In particular, the present invention relates to a method for rapidly identifying porcine estrogen receptor marker by means of mutagenically separated polymerase chain reaction (MSPCR).
2. Description of the Related Art
It is a trend to raise as many pigs as possible in a limited area to improve the productivity. Improvement in the productivity of female pigs will definitely decrease the cost and increase the competitiveness. In addition to breeding, a marker-assisted selection has been used to sort pigs with high productivity. The number of pups for a female pig at each birth is an important index for its propagating capability. Researches in the genes affecting the number of pups are undergoing, and examples of which are disclosed in “Estrogen Receptor Gene, ESR,” Rothschild et al., Anim. Genet, Volume 22, page 448, 1991; Proc. 5th World Congr. Gene t. Appli. Livest. Prod. Volume 21, pages 225-228, 1994; Proc. Natl. Acad. Sci. USA, Volume 93, pages 201-205, 1996; Short et al., J. Anim. Sci. Volume 73, (Suppl. 1), page 109 (Abstr.), 1995; J. Anim. Sci. Volume 7-5 (Journal 12), pages 3138-3142, 1997; “Major Histocompatibility Complex Genes, MHC,” Warner and Rothschild, Immunogenetics of the MHC, pages 368-397, VCH Publishers, New York, USA, 1991; and “Osteopontin Marker, OPN,” Short et al., J. Anim. Sci. Volume 75 (Suppl. 1), page 29 (Abstr.), 1997. All of these documents are related to propagating capability.
The ESR gene on the short arm of the No. 1 chromosome comprises two alleles A and B. According to research, the allele B is the primary gene for the productivity of the “May-San” pigs. When existing in homozygote state, the major histocompatibility complex genes (MHC) shall adversely affect survival of the embryos. The genotypes of the osteopontin markers (OPN) affect the total number of pups at a birth and the number of survival pups, wherein one of five alternate genes relates to the total number of pups at a birth, and the other four alternate genes relate to the number of survival pups. According to research, the survival rate of pups from the first birth through the sixth birth is relatively high for female pigs of OPN hetero-genotype. (Liao, Zen-Po et al., Chinese Livestock Magazine, Volume 28(1), pages 33-39, 1999).
According to Applicant's own research in examination of the pigs in the slaughterhouses, no homozygote with allele B was found, and the percentage of zygote with allele AB was 17.8%; namely, not many studpigs in Taiwan As possess allele B. According to research in the studpigs, the estrogen receptor (ESR) inheriting marker is indeed relevant to the propagating capability. According to primary research, the survival pigs bred by a female pig with prolific genotype was higher than those bred by a female pig without prolific genotype by 0.39 at the first birth, and by 0.31 at each subsequent birth. Thus, it would be able to reduce the number of new spare studpigs that have to be raised while achieving the same productivity, reducing the cost, and improving the competitiveness if the estrogen receptor genotype of each pig can be identified when it is still a pup. Currently in the art, polymerase chain reaction and restriction cut reaction are used to fragment DNA to thereby identify the genotype of pigs, but it is time consuming and costly.